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Digging for Clues with Geological Phenomena

March 17, 2011

By Tara Laskowski

Sheryl Beach

Deep in a valley in southeastern Iceland, Mason hydrologist Sheryl Beach spent days hiking over miles of hardened lava searching for evidence.

She and her research team examined rocks, water, sand, and volcanic ash in that Martian-looking landscape, searching for clues of a mega flood of biblical proportion—a phenomenon so powerful it changed the face of the planet. And they found those clues.

On that trip to Iceland in 2008, Beach, Mason PhD student Douglas Howard, and Georgetown University geomorphology professor Tim Beach found evidence of a jökulhlaup, a catastrophic release of glacial floodwaters caused when volcanic activity, similar to the volcanic outburst in early 2010 that disrupted air travel around the world, melts glaciers on top of mountains.

The team, supported by a grant from the National Science Foundation, had three objectives in Iceland: To look for evidence of a mega flood, to model that flood to determine its power and volume, and to compare the landscape features shaped by the flood with similar watershed basins on the planet Mars.

Douglas Howard and Sheryl Beach in Iceland

The results were more than any of them could have hoped for. In fact, their evidence suggests this mega flood, which appears to date back more than 8,000 years, was the largest of this type on Earth.

“The sheer power of this flood makes it the largest we’ve ever seen,” says Howard, who completed his PhD in earth systems and geoinformation sciences in 2009 and is now full time with the U.S. Geological Survey. “It may not be the largest spatially, but it was the most forceful.”

Howard, a planetary geologist, is most interested in looking at how these floods can help him learn something about the landscape of the planet Mars. He has developed a hydrologic model that calculated the areal extent and the peak discharge of the flood. With this model, he was able to reconstruct the event and calculate how deep the channel was and how fast the water was going when the glacier burst.

Beach and Howard's research suggests this is the channel where the mega flood occurred.

“In following the footsteps of other researchers who have looked at this channel, we discovered through our field work that there had been a much greater flood than people had calculated before,” says Beach, an associate professor of geography and geoinformation science at Mason. Beach’s research focuses on the history of landscapes and how the Earth has changed over time. Beach and her husband and co-author, Tim Beach, were recently recognized with the 2010 G. K. Gilbert Excellence in Geomorphological Research Award by the Association of American Geographers.

Glacial outburst floods, as opposed to river floods, are much more powerful and destructive to the landscape, says Beach. “The cutting power of a glacial flood is like a bulldozer. It takes rocks with it, plows through the sides of mountains, and picks material up and deposits it in a particular way.”

Glacial ice makes a U-shaped valley, such as Yosemite Valley in California, as it flows. River valleys are often V-shaped because a river cuts them down more vertically over time and then deposits the materials in a well-sorted, orderly manner.

In the case of the Jokulsá á Fjöllum river channel in Iceland, Beach and the team found well-sorted rocks on top of a hill that didn’t match the hill. But the rocks did match an area across the channel that had been gouged out.

“It looked like someone had taken a gigantic fire hose, blasted the side of the mountain, flipped its rocks across the channel and sorted them out on the other side,” she says. “We said to ourselves, ‘That’s what a mega flood looks like.’”

With this new evidence, Beach and Howard hope to prove to the world that the Jokulsá á Fjöllum mega flood was the largest in history. The team has written a paper on its findings, which will be published in a future issue of the journal Geomorphology. They hope their results will help scientists in the future looking at these phenomena—both on our planet and elsewhere in the universe.

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